Before you start sewing the skirt, test the thread tension with a spare piece of fabric of a similar thickness and texture to that of the skirt. (Your zigzag stitches should look like the second image on the left.)

Then, sew along the traced line.

6. Repeat the previous steps on the back half of the skirt, making sure that the crotch end of the back curve and the crotch end of the front curve are the same distance from the hem (the distances marked in green in the image).

7. At this point, remove the sewing pins and try on the skirt to see whether the new seam lines fit you well. When doing so, hold the front and back layers together at the crotch to simulate a pair of shorts.

After making sure that you are happy with the seams, trim off the excess fabric along both of the seams, very close to, but not touching, the zigzag stitches.

8. Place the shorts on top of the front half of the skirt again, aligning their front curves.

9. Trace the inseam of the shorts onto the skirt, making sure that the line’s top edge meets the end of the front seam that you just sewed (indicated by the green arrow).

10. Insert a sewing pin along the line you just traced to hold the two layers of the skirt together. (Note: It is important that the sewing pin is aligned with the line.)

Then cut along the side edge of the skirt from the hem up to the crotch end of the seam, as shown with blue dots in the image.

11. On the reverse side, draw another inseam line. Here, you need to trace the direction of the sewing pin that you inserted in the previous step to copy the first inseam line.

12. Now, on the back half of the skirt, pin the two layers together. You do not need to draw inseam lines here. Simply make a cut along the side edge of the fold, as you did in Step 10 (along the blue dots).

13. Remove all of the sewing pins and refold the skirt, this time with its front layer on top of its back layer.

Align the front and back layers at the crotch, and pin them together along the inseam lines (which are highlighted in green). As you can see, the two lines connect at the crotch, making a V shape.

14. Sew along the V-shaped line, starting from one end, through the crotch and all the way to the other end.

15. Trim off the excess fabric by cutting along the stitching that you just made. Again, be careful not to cut the stitches.